<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
+ <meta encoding="utf8">
<link rel="stylesheet" href="llvm.css" type="text/css">
- <title>LLVM 2.7 Release Notes</title>
+ <title>LLVM 2.9 Release Notes</title>
</head>
<body>
-<div class="doc_title">LLVM 2.7 Release Notes</div>
+<div class="doc_title">LLVM 2.9 Release Notes</div>
<img align=right src="http://llvm.org/img/DragonSmall.png"
width="136" height="136" alt="LLVM Dragon Logo">
<ol>
<li><a href="#intro">Introduction</a></li>
<li><a href="#subproj">Sub-project Status Update</a></li>
- <li><a href="#externalproj">External Projects Using LLVM 2.7</a></li>
- <li><a href="#whatsnew">What's New in LLVM 2.7?</a></li>
+ <li><a href="#externalproj">External Projects Using LLVM 2.9</a></li>
+ <li><a href="#whatsnew">What's New in LLVM 2.9?</a></li>
<li><a href="GettingStarted.html">Installation Instructions</a></li>
- <li><a href="#portability">Portability and Supported Platforms</a></li>
<li><a href="#knownproblems">Known Problems</a></li>
<li><a href="#additionalinfo">Additional Information</a></li>
</ol>
<p>Written by the <a href="http://llvm.org">LLVM Team</a></p>
</div>
-<!--
-<h1 style="color:red">These are in-progress notes for the upcoming LLVM 2.8
+<h1 style="color:red">These are in-progress notes for the upcoming LLVM 2.9
release.<br>
You may prefer the
-<a href="http://llvm.org/releases/2.6/docs/ReleaseNotes.html">LLVM 2.7
-Release Notes</a>.</h1>-->
+<a href="http://llvm.org/releases/2.8/docs/ReleaseNotes.html">LLVM 2.8
+Release Notes</a>.</h1>
<!-- *********************************************************************** -->
<div class="doc_section">
<div class="doc_text">
<p>This document contains the release notes for the LLVM Compiler
-Infrastructure, release 2.7. Here we describe the status of LLVM, including
+Infrastructure, release 2.9. Here we describe the status of LLVM, including
major improvements from the previous release and significant known problems.
All LLVM releases may be downloaded from the <a
href="http://llvm.org/releases/">LLVM releases web site</a>.</p>
<a href="http://llvm.org/releases/">releases page</a>.</p>
</div>
-
+
+<!-- NOTE: last release for llvm-gcc -->
<!--
Almost dead code.
- include/llvm/Analysis/LiveValues.h => Dan
- lib/Transforms/IPO/MergeFunctions.cpp => consider for 2.8.
- llvm/Analysis/PointerTracking.h => Edwin wants this, consider for 2.8.
- ABCD, GEPSplitterPass
- MSIL backend?
- lib/Transforms/Utils/SSI.cpp -> ABCD depends on it.
+ lib/Transforms/IPO/MergeFunctions.cpp => consider for 3.0.
-->
-<!-- Features that need text if they're finished for 2.7:
+<!-- Features that need text if they're finished for 3.0:
combiner-aa?
strong phi elim
- llvm.dbg.value: variable debug info for optimized code
loop dependence analysis
+ TBAA
+ CorrelatedValuePropagation
-->
-
- <!-- for announcement email:
- Logo web page.
- llvm devmtg
- compiler_rt
- KLEE web page at klee.llvm.org
- Many new papers added to /pubs/
- Mention gcc plugin.
- -->
-
+
<!-- *********************************************************************** -->
<div class="doc_section">
<a name="subproj">Sub-project Status Update</a>
<div class="doc_text">
<p>
-The LLVM 2.7 distribution currently consists of code from the core LLVM
+The LLVM 2.9 distribution currently consists of code from the core LLVM
repository (which roughly includes the LLVM optimizers, code generators
and supporting tools), the Clang repository and the llvm-gcc repository. In
addition to this code, the LLVM Project includes other sub-projects that are in
<div class="doc_text">
-<p>The <a href="http://clang.llvm.org/">Clang project</a> is ...</p>
+<p><a href="http://clang.llvm.org/">Clang</a> is an LLVM front end for the C,
+C++, and Objective-C languages. Clang aims to provide a better user experience
+through expressive diagnostics, a high level of conformance to language
+standards, fast compilation, and low memory use. Like LLVM, Clang provides a
+modular, library-based architecture that makes it suitable for creating or
+integrating with other development tools. Clang is considered a
+production-quality compiler for C, Objective-C, C++ and Objective-C++ on x86
+(32- and 64-bit), and for darwin-arm targets.</p>
-<p>In the LLVM 2.7 time-frame, the Clang team has made many improvements:</p>
+<p>In the LLVM 2.9 time-frame, the Clang team has made many improvements:</p>
<ul>
-<li>FIXME: C++! Include a link to cxx_compatibility.html</li>
-
-<li>CIndex API and Python bindings: Clang now includes a C API as part of the
-CIndex library. Although we make make some changes to the API in the future, it
-is intended to be stable and has been designed for use by external projects. See
-the Clang
-doxygen <a href="http://clang.llvm.org/doxygen/group__CINDEX.html">CIndex</a>
-documentation for more details. The CIndex API also includings an preliminary
-set of Python bindings.</li>
-
-<li>ARM Support: Clang now has ABI support for both the Darwin and Linux ARM
-ABIs. Coupled with many improvements to the LLVM ARM backend, Clang is now
-suitable for use as a a beta quality ARM compiler.</li>
</ul>
</div>
future</a>!). The tool is very good at finding bugs that occur on specific
paths through code, such as on error conditions.</p>
-<p>In the LLVM 2.7 time-frame, the analyzer core has made several major and
- minor improvements, including better support for tracking the fields of
- structures, initial support (not enabled by default yet) for doing
- interprocedural (cross-function) analysis, and new checks have been added.
+<p>The LLVM 2.9 release...
</p>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
-<a name="vmkit">VMKit: JVM/CLI Virtual Machine Implementation</a>
+<a name="dragonegg">DragonEgg: llvm-gcc ported to gcc-4.5</a>
</div>
<div class="doc_text">
+NOTE: This should be written to be self-contained without referencing llvm-gcc.
+
<p>
-The <a href="http://vmkit.llvm.org/">VMKit project</a> is an implementation of
-a JVM and a CLI Virtual Machine (Microsoft .NET is an
-implementation of the CLI) using LLVM for static and just-in-time
-compilation.</p>
+<a href="http://dragonegg.llvm.org/">DragonEgg</a> is a port of llvm-gcc to
+gcc-4.5. Unlike llvm-gcc, dragonegg in theory does not require any gcc-4.5
+modifications whatsoever (currently one small patch is needed) thanks to the
+new <a href="http://gcc.gnu.org/wiki/plugins">gcc plugin architecture</a>.
+DragonEgg is a gcc plugin that makes gcc-4.5 use the LLVM optimizers and code
+generators instead of gcc's, just like with llvm-gcc.
+</p>
<p>
-With the release of LLVM 2.7, VMKit has shifted to a great framework for writing
-virtual machines. VMKit now offers precise and efficient garbage collection with
-multi-threading support, thanks to the MMTk memory management toolkit, as well
-as just in time and ahead of time compilation with LLVM. The major changes in
-VMKit 0.27 are:</p>
+DragonEgg is still a work in progress, but it is able to compile a lot of code,
+for example all of gcc, LLVM and clang. Currently Ada, C, C++ and Fortran work
+well, while all other languages either don't work at all or only work poorly.
+For the moment only the x86-32 and x86-64 targets are supported, and only on
+linux and darwin (darwin may need additional gcc patches).
+</p>
+<p>
+The 2.9 release has the following notable changes:
<ul>
+</ul>
-<li>Garbage collection: VMKit now uses the MMTk toolkit for garbage collectors.
- The first collector to be ported is the MarkSweep collector, which is precise,
- and drastically improves the performance of VMKit.</li>
-<li>Line number information in the JVM: by using the debug metadata of LLVM, the
- JVM now supports precise line number information, useful when printing a stack
- trace.</li>
-<li>Interface calls in the JVM: we implemented a variant of the Interface Method
- Table technique for interface calls in the JVM.
-</li>
+</div>
-</ul>
+<!--=========================================================================-->
+<div class="doc_subsection">
+<a name="vmkit">VMKit: JVM Virtual Machine Implementation</a>
</div>
+<div class="doc_text">
+<p>
+The <a href="http://vmkit.llvm.org/">VMKit project</a> is an implementation of
+a Java Virtual Machine (Java VM or JVM) that uses LLVM for static and
+just-in-time compilation.
+
+UPDATE.
+</p>
+</div>
<!--=========================================================================-->
<div class="doc_subsection">
<p>
All of the code in the compiler-rt project is available under the standard LLVM
-License, a "BSD-style" license. New in LLVM 2.7: compiler_rt now
-supports ARM targets.</p>
+License, a "BSD-style" license.
+
+NEW: MIT License as well.
+
+New in LLVM 2.9, UPDATE</p>
</div>
<!--=========================================================================-->
<div class="doc_subsection">
-<a name="dragonegg">DragonEgg: llvm-gcc ported to gcc-4.5</a>
+<a name="lldb">LLDB: Low Level Debugger</a>
</div>
<div class="doc_text">
<p>
-<a href="http://dragonegg.llvm.org/">DragonEgg</a> is a port of llvm-gcc to
-gcc-4.5. Unlike llvm-gcc, which makes many intrusive changes to the underlying
-gcc-4.2 code, dragonegg in theory does not require any gcc-4.5 modifications
-whatsoever (currently one small patch is needed). This is thanks to the new
-<a href="http://gcc.gnu.org/wiki/plugins">gcc plugin architecture</a>, which
-makes it possible to modify the behaviour of gcc at runtime by loading a plugin,
-which is nothing more than a dynamic library which conforms to the gcc plugin
-interface. DragonEgg is a gcc plugin that causes the LLVM optimizers to be run
-instead of the gcc optimizers, and the LLVM code generators instead of the gcc
-code generators, just like llvm-gcc. To use it, you add
-"-fplugin=path/dragonegg.so" to the gcc-4.5 command line, and gcc-4.5 magically
-becomes llvm-gcc-4.5!
-</p>
+<a href="http://lldb.llvm.org/">LLDB</a> is a brand new member of the LLVM
+umbrella of projects. LLDB is a next generation, high-performance debugger. It
+is built as a set of reusable components which highly leverage existing
+libraries in the larger LLVM Project, such as the Clang expression parser, the
+LLVM disassembler and the LLVM JIT.</p>
<p>
-DragonEgg is still a work in progress. Currently C works very well, while C++,
-Ada and Fortran work fairly well. All other languages either don't work at all,
-or only work poorly. For the moment only the x86-32 and x86-64 targets are
-supported, and only on linux and darwin (darwin needs an additional gcc patch).
-</p>
+LLDB is in early development and not included as part of the LLVM 2.9 release,
+UPDATE!
-<p>
-DragonEgg is a new project which is seeing its first release with llvm-2.7.
+<!--
+but is mature enough to support basic debugging scenarios on Mac OS X in C,
+Objective-C and C++. We'd really like help extending and expanding LLDB to
+support new platforms, new languages, new architectures, and new features.-->
</p>
</div>
-
<!--=========================================================================-->
<div class="doc_subsection">
-<a name="mc">llvm-mc: Machine Code Toolkit</a>
+<a name="libc++">libc++: C++ Standard Library</a>
</div>
<div class="doc_text">
<p>
-The LLVM Machine Code (aka MC) sub-project of LLVM was created to solve a number
-of problems in the realm of assembly, disassembly, object file format handling,
-and a number of other related areas that CPU instruction-set level tools work
-in. It is a sub-project of LLVM which provides it with a number of advantages
-over other compilers that do not have tightly integrated assembly-level tools.
-For a gentle introduction, please see the <a
-href="http://blog.llvm.org/2010/04/intro-to-llvm-mc-project.html">Intro to the
-LLVM MC Project Blog Post</a>.
-</p>
-
-<p>2.7 includes major parts of the work required by the new MC Project. A few
- targets have been refactored to support it, and work is underway to support a
- native assembler in LLVM. This work is not complete in LLVM 2.7, but you has
- made substantially more progress on LLVM mainline.</p>
-
-<p>One minor example of what MC can do is to transcode an AT&T syntax
- X86 .s file into intel syntax. You can do this with something like:</p>
-<pre>
- llvm-mc foo.s -output-asm-variant=1 -o foo-intel.s
-</pre>
-
-</div>
-
-
-<!-- *********************************************************************** -->
-<div class="doc_section">
- <a name="externalproj">External Open Source Projects Using LLVM 2.7</a>
-</div>
-<!-- *********************************************************************** -->
+<a href="http://libcxx.llvm.org/">libc++</a> is another new member of the LLVM
+family. It is an implementation of the C++ standard library, written from the
+ground up to specifically target the forthcoming C++'0X standard and focus on
+delivering great performance.</p>
-<div class="doc_text">
+<p>
+As of the LLVM 2.9 release, UPDATE!
-<p>An exciting aspect of LLVM is that it is used as an enabling technology for
- a lot of other language and tools projects. This section lists some of the
- projects that have already been updated to work with LLVM 2.7.</p>
-</div>
+<!--libc++ is virtually feature complete, but would
+benefit from more testing and better integration with Clang++. It is also
+looking forward to the C++ committee finalizing the C++'0x standard.-->
+</p>
-<!--=========================================================================-->
-<div class="doc_subsection">
-<a name="pure">Pure</a>
</div>
-<div class="doc_text">
-<p>
-<a href="http://pure-lang.googlecode.com/">Pure</a>
-is an algebraic/functional programming language based on term rewriting.
-Programs are collections of equations which are used to evaluate expressions in
-a symbolic fashion. Pure offers dynamic typing, eager and lazy evaluation,
-lexical closures, a hygienic macro system (also based on term rewriting),
-built-in list and matrix support (including list and matrix comprehensions) and
-an easy-to-use C interface. The interpreter uses LLVM as a backend to
- JIT-compile Pure programs to fast native code.</p>
-
-<p>Pure versions 0.43 and later have been tested and are known to work with
-LLVM 2.7 (and continue to work with older LLVM releases >= 2.5).</p>
-</div>
<!--=========================================================================-->
<div class="doc_subsection">
-<a name="RoadsendPHP">Roadsend PHP</a>
+<a name="klee">KLEE: A Symbolic Execution Virtual Machine</a>
</div>
<div class="doc_text">
<p>
-<a href="http://code.roadsend.com/rphp">Roadsend PHP</a> (rphp) is an open
-source implementation of the PHP programming
-language that uses LLVM for its optimizer, JIT and static compiler. This is a
-reimplementation of an earlier project that is now based on LLVM.
+<a href="http://klee.llvm.org/">KLEE</a> is a symbolic execution framework for
+programs in LLVM bitcode form. KLEE tries to symbolically evaluate "all" paths
+through the application and records state transitions that lead to fault
+states. This allows it to construct testcases that lead to faults and can even
+be used to verify some algorithms.
</p>
-</div>
-<!--=========================================================================-->
-<div class="doc_subsection">
-<a name="UnladenSwallow">Unladen Swallow</a>
-</div>
+<p>UPDATE!</p>
-<div class="doc_text">
-<p>
-<a href="http://code.google.com/p/unladen-swallow/">Unladen Swallow</a> is a
-branch of <a href="http://python.org/">Python</a> intended to be fully
-compatible and significantly faster. It uses LLVM's optimization passes and JIT
-compiler.
-</p>
</div>
-<!--=========================================================================-->
-<div class="doc_subsection">
-<a name="tce">TTA-based Codesign Environment (TCE)</a>
+
+<!-- *********************************************************************** -->
+<div class="doc_section">
+ <a name="externalproj">External Open Source Projects Using LLVM 2.9</a>
</div>
+<!-- *********************************************************************** -->
<div class="doc_text">
-<p>
-<a href="http://tce.cs.tut.fi/">TCE</a> is a toolset for designing
-application-specific processors (ASP) based on the Transport triggered
-architecture (TTA). The toolset provides a complete co-design flow from C/C++
-programs down to synthesizable VHDL and parallel program binaries. Processor
-customization points include the register files, function units, supported
-operations, and the interconnection network.</p>
-
-<p>TCE uses llvm-gcc/Clang and LLVM for C/C++ language support, target
-independent optimizations and also for parts of code generation. It generates
-new LLVM-based code generators "on the fly" for the designed TTA processors and
-loads them in to the compiler backend as runtime libraries to avoid per-target
-recompilation of larger parts of the compiler chain.</p>
+<p>An exciting aspect of LLVM is that it is used as an enabling technology for
+ a lot of other language and tools projects. This section lists some of the
+ projects that have already been updated to work with LLVM 2.9.</p>
</div>
-<!--=========================================================================-->
-<div class="doc_subsection">
-<a name="safecode">SAFECode Compiler</a>
-</div>
-<div class="doc_text">
-<p>
-<a href="http://safecode.cs.illinois.edu">SAFECode</a> is a memory safe C
-compiler built using LLVM. It takes standard, unannotated C code, analyzes the
-code to ensure that memory accesses and array indexing operations are safe, and
-instruments the code with run-time checks when safety cannot be proven
-statically.
-</p>
-</div>
<!-- *********************************************************************** -->
<div class="doc_section">
- <a name="whatsnew">What's New in LLVM 2.7?</a>
+ <a name="whatsnew">What's New in LLVM 2.9?</a>
</div>
<!-- *********************************************************************** -->
</div>
-<!--=========================================================================-->
-<div class="doc_subsection">
-<a name="orgchanges">LLVM Community Changes</a>
-</div>
-
-<div class="doc_text">
-
-<p>In addition to changes to the code, between LLVM 2.6 and 2.7, a number of
-organization changes have happened:
-</p>
-
-<ul>
-<li>LLVM has a new <a href="http://llvm.org/Logo.html">official logo</a>!</li>
-
-<li>Ted Kremenek and Doug Gregor have stepped forward as <a
- href="http://llvm.org/docs/DeveloperPolicy.html#owners">Code Owners</a> of the
- Clang static analyzer and the Clang frontend, respectively.</li>
-
-<li>LLVM now has an <a href="http://blog.llvm.org">official Blog</a> at
- <a href="http://blog.llvm.org">http://blog.llvm.org</a>. This is a great way
- to learn about new LLVM-related features as they are implemented. Several
- features in this release are already explained on the blog.</li>
-
-<li>The LLVM web pages are now checked into the SVN server, in the "www",
- "www-pubs" and "www-releases" SVN modules. Previously they were hidden in a
- largely inaccessible old CVS server.</li>
-
-<li><a href="http://llvm.org">llvm.org</a> is now hosted on a new (and much
- faster) server. It is still graciously hosted at the University of Illinois
- of Urbana Champaign.</li>
-</ul>
-</div>
-
<!--=========================================================================-->
<div class="doc_subsection">
<a name="majorfeatures">Major New Features</a>
<div class="doc_text">
-<p>LLVM 2.7 includes several major new capabilities:</p>
+<p>LLVM 2.9 includes several major new capabilities:</p>
<ul>
-<li>2.7 includes initial support for the <a
- href="http://en.wikipedia.org/wiki/MicroBlaze">MicroBlaze</a> target.
- MicroBlaze is a soft processor core designed for Xilinx FPGAs.</li>
-
-<li>2.7 includes a new LLVM IR "extensible metadata" feature. This feature
- supports many different use cases, including allowing front-end authors to
- encode source level information into LLVM IR, which is consumed by later
- language-specific passes. This is a great way to do high-level optimizations
- like devirtualization, type-based alias analysis, etc. See the <a
- href="http://blog.llvm.org/2010/04/extensible-metadata-in-llvm-ir.html">
- Extensible Metadata Blog Post</a> for more information.</li>
-
-<li>2.7 encodes <a href="SourceLevelDebugging.html">debug information</a>
-in a completely new way, built on extensible metadata. The new implementation
-is much more memory efficient and paves the way for improvements to optimized
-code debugging experience.</li>
-
-<li>2.7 now directly supports taking the address of a label and doing an
- indirect branch through a pointer. This is particularly useful for
- interpreter loops, and is used to implement the GCC "address of label"
- extension. For more information, see the <a
-href="http://blog.llvm.org/2010/01/address-of-label-and-indirect-branches.html">
-Address of Label and Indirect Branches in LLVM IR Blog Post</a>.
-
-<li>2.7 is the first release to start supporting APIs for assembling and
- disassembling target machine code. These APIs are useful for a variety of
- low level clients, and are surfaced in the new "enhanced disassembly" API.
- For more information see the <a
- href="http://blog.llvm.org/2010/01/x86-disassembler.html">The X86
- Disassembler Blog Post</a> for more information.</li>
-
-<li>2.7 includes major parts of the work required by the new MC Project,
- see the <a href="#mc">MC update above</a> for more information.</li>
-
</ul>
</div>
expose new optimization opportunities:</p>
<ul>
-<li>LLVM IR now supports a 16-bit "half float" data type through <a
- href="LangRef.html#int_fp16">two new intrinsics</a> and APFloat support.</li>
-<li>LLVM IR supports two new <a href="LangRef.html#fnattrs">function
- attributes</a>: inlinehint and alignstack(n). The former is a hint to the
- optimizer that a function was declared 'inline' and thus the inliner should
- weight it higher when considering inlining it. The later
- indicates to the code generator that the function diverges from the platform
- ABI on stack alignment.</li>
-<li>The new <a href="LangRef.html#int_objectsize">llvm.objectsize</a> intrinsic
- allows the optimizer to infer the sizes of memory objects in some cases.
- This intrinsic is used to implement the GCC <tt>__builtin_object_size</tt>
- extension.</li>
-<li>LLVM IR now supports marking load and store instructions with <a
- href="LangRef.html#i_load">"non-temporal" hints</a> (building on the new
- metadata feature). This hint encourages the code
- generator to generate non-temporal accesses when possible, which are useful
- for code that is carefully managing cache behavior. Currently, only the
- X86 backend provides target support for this feature.</li>
-
-<li>LLVM 2.7 has pre-alpha support for <a
- href="LangRef.html#t_union">unions in LLVM IR</a>.
- Unfortunately, this support is not really usable in 2.7, so if you're
- interested in pushing it forward, please help contribute to LLVM mainline.</li>
-
</ul>
</div>
release includes a few major enhancements and additions to the optimizers:</p>
<ul>
-
-<li>The inliner reuses now merges arrays stack objects in different callees when
- inlining multiple call sites into one function. This reduces the stack size
- of the resultant function.</li>
-<li>The -basicaa alias analysis pass (which is the default) has been improved to
- be less dependent on "type safe" pointers. It can now look through bitcasts
- and other constructs more aggressively, allowing better load/store
- optimization.</li>
-<li>The load elimination optimization in the GVN Pass [<a
-href="http://blog.llvm.org/2009/12/introduction-to-load-elimination-in-gvn.html">intro
- blog post</a>] has been substantially improved to be more aggressive about
- partial redundancy elimination and do more aggressive phi translation. Please
- see the <a
- href="http://blog.llvm.org/2009/12/advanced-topics-in-redundant-load.html">
- Advanced Topics in Redundant Load Elimination with a Focus on PHI Translation
- Blog Post</a> for more details.</li>
-<li>The module <a href="LangRef.html#datalayout">target data string</a> now
- includes a notion of 'native' integer data types for the target. This
- helps mid-level optimizations avoid promoting complex sequences of
- operations to data types that are not natively supported (e.g. converting
- i32 operations to i64 on 32-bit chips).</li>
-<li>The mid-level optimizer is now conservative when operating on a module with
- no target data. Previously, it would default to SparcV9 settings, which is
- not what most people expected.</li>
-<li>Jump threading is now much more aggressive at simplifying correlated
- conditionals and threading blocks with otherwise complex logic. It has
- subsumed the old "Conditional Propagation" pass, and -condprop has been
- removed from LLVM 2.7.</li>
-<li>The -instcombine pass has been refactored from being one huge file to being
- a library of its own. Internally, it uses a customized IRBuilder to clean
- it up and simplify it.</li>
-
-<li>The optimal edge profiling pass is reliable and much more complete than in
- 2.6. It can be used with the llvm-prof tool but isn't wired up to the
- llvm-gcc and clang command line options yet.</li>
-
-<li>A new experimental alias analysis implementation, -scev-aa, has been added.
- It uses LLVM's Scalar Evolution implementation to do symbolic analysis of
- pointer offset expressions to disambiguate pointers. It can catch a few
- cases that basicaa cannot, particularly in complex loop nests.</li>
-
-<li>The default pass ordering has been tweaked for improved optimization
- effectiveness.</li>
-
+ <li>TBAA.</li>
+ <li>LTO has been improved to use MC for parsing inline asm and now
+ can build large programs like Firefox 4 on both OS X and Linux.</li>
</ul>
-</div>
+<!--
+<p>In addition to these features that are done in 2.8, there is preliminary
+ support in the release for Type Based Alias Analysis
+ Preliminary work on TBAA but not usable in 2.8.
+ New CorrelatedValuePropagation pass, not on by default in 2.8 yet.
+-->
+</div>
<!--=========================================================================-->
<div class="doc_subsection">
-<a name="executionengine">Interpreter and JIT Improvements</a>
+<a name="mc">MC Level Improvements</a>
</div>
<div class="doc_text">
+<p>
+The LLVM Machine Code (aka MC) subsystem was created to solve a number
+of problems in the realm of assembly, disassembly, object file format handling,
+and a number of other related areas that CPU instruction-set level tools work
+in.</p>
<ul>
-<li>The JIT now supports generating debug information and is compatible with
-the new GDB 7.0 (and later) interfaces for registering dynamically generated
-debug info.</li>
-
-<li>The JIT now <a href="http://llvm.org/PR5184">defaults
-to compiling eagerly</a> to avoid a race condition in the lazy JIT.
-Clients that still want the lazy JIT can switch it on by calling
-<tt>ExecutionEngine::DisableLazyCompilation(false)</tt>.</li>
+ <li>MC is now used by default for ELF systems on x86 and
+ x86-64.</li>
+ <li>MC supports and CodeGen uses the <tt>.loc</tt> directives for
+ producing line number debug info. This produces more compact line
+ tables.</li>
+ <li>MC supports the <tt>.cfi_*</tt> directives for producing DWARF
+ frame information, but it is still not used by CodeGen by default.</li>
+ <li>COFF support?</li>
+</ul>
-<li>It is now possible to create more than one JIT instance in the same process.
-These JITs can generate machine code in parallel,
-although <a href="http://llvm.org/docs/ProgrammersManual.html#jitthreading">you
-still have to obey the other threading restrictions</a>.</li>
+<p>For more information, please see the <a
+href="http://blog.llvm.org/2010/04/intro-to-llvm-mc-project.html">Intro to the
+LLVM MC Project Blog Post</a>.
+</p>
-</ul>
+</div>
-</div>
<!--=========================================================================-->
<div class="doc_subsection">
it run faster:</p>
<ul>
-<li>The 'llc -asm-verbose' option (which is now the default) has been enhanced
- to emit many useful comments to .s files indicating information about spill
- slots and loop nest structure. This should make it much easier to read and
- understand assembly files. This is wired up in llvm-gcc and clang to
- the <tt>-fverbose-asm</tt> option.</li>
-
-<li>New LSR with "full strength reduction" mode. FIXME: Description?</li>
-
-<li>A new codegen level Common Subexpression Elimination pass (MachineCSE)
- is available and enabled by default. It catches redundancies exposed by
- lowering.</li>
-<li>A new pre-register-allocation tail duplication pass is available and enabled
- by default, it can substantially improve branch prediction quality in some
- cases.</li>
-<li>A new sign and zero extension optimization pass (OptimizeExtsPass)
- is available and enabled by default. This pass can takes advantage
- architecture features like x86-64 implicit zero extension behavior and
- sub-registers.</li>
-<li>The code generator now supports a mode where it attempts to preserve the
- order of instructions in the input code. This is important for source that
- is hand scheduled and extremely sensitive to scheduling. It is compatible
- with the GCC <tt>-fno-schedule-insns</tt> option.</li>
-<li>The target-independent code generator now supports generating code with
- arbitrary numbers of result values. Returning more values than was
- previously supported is handled by returning through a hidden pointer. In
- 2.7, only the X86 and XCore targets have adopted support for this
- though.</li>
-<li>The code generator now supports generating code that follows the
- <a href="LangRef.html#callingconv">Glasgow Haskell Compiler Calling
- Convention</a> and ABI.</li>
-<li>The "<a href="CodeGenerator.html#selectiondag_select">DAG instruction
- selection</a>" phase of the code generator has been largely rewritten for
- 2.7. Previously, tblgen spit out tons of C++ code which was compiled and
- linked into the target to do the pattern matching, now it emits a much
- smaller table which is read by the target-independent code. The primary
- advantages of this approach is that the size and compile time of various
- targets is much improved. The X86 code generator shrunk by 1.5MB of code,
- for example.</li>
-<li>Almost the entire code generator has switched to emitting code through the
- MC interfaces instead of printing textually to the .s file. This led to a
- number of cleanups and speedups. In 2.7, debug an exception handling
- information does not go through MC yet.</li>
+<!-- SplitKit -->
+FastISel for ARM.
</ul>
</div>
</div>
<div class="doc_text">
-<p>New features of the X86 target include:
+<p>New features and major changes in the X86 target include:
</p>
<ul>
-<li>The X86 backend now optimizes tails calls much more aggressively for
- functions that use the standard C calling convention.</li>
-<li>The X86 backend now models scalar SSE registers as subregs of the SSE vector
- registers, making the code generator more aggressive in cases where scalars
- and vector types are mixed.</li>
-
-<li>PostRA scheduler for X86? FIXME: is this on by default in 2.7?</li>
-
</ul>
</div>
</p>
<ul>
-
-<li>The ARM backend now generates instructions in unified assembly syntax.</li>
-
-<li>llvm-gcc now has complete support for the ARM v7 NEON instruction set. This
- support differs slightly from the GCC implementation. Please see the
- <a
-href="http://blog.llvm.org/2010/04/arm-advanced-simd-neon-intrinsics-and.html">
- ARM Advanced SIMD (NEON) Intrinsics and Types in LLVM Blog Post</a> for
- helpful information if migrating code from GCC to LLVM-GCC.</li>
-
-<li>The ARM and Thumb code generators now using register scavenging for stack
- object address materialization.(FIXME: WHAT BENEFIT DOES THIS PROVIDE?)</li>
-
-<li>The ARM backend now has good support for ARMv4 targets, and has been tested
- on StrongARM hardware. Previously, LLVM only supported ARMv4T and
- newer chips.</li>
-</ul>
-
-
-</div>
-
-<!--=========================================================================-->
-<div class="doc_subsection">
-<a name="newapis">New Useful APIs</a>
-</div>
-
-<div class="doc_text">
-
-<p>This release includes a number of new APIs that are used internally, which
- may also be useful for external clients.
-</p>
-
-<ul>
-<li>The optimizer uses the new CodeMetrics class to measure the size of code.
- Various passes that use thing (like the inliner, loop unswitcher, etc) all
- use this to make more accurate estimates of the code size impact of various
- optimizations.</li>
-<li>A new <a href="http://llvm.org/doxygen/InstructionSimplify_8h-source.html">
- llvm/Analysis/InstructionSimplify.h</a> interface available for doing
- symbolic simplification of instructions (e.g. <tt>a+0</tt> -> <tt>a</tt>)
- without requiring the instruction to exist. This centralizes a lot of
- ad-hoc symbolic manipulation code scattered in various passes.</li>
-<li>The optimizer now uses a new <a
- href="http://llvm.org/doxygen/SSAUpdater_8h-source.html">SSAUpdater</a>
- class which efficiently supports
- doing unstructured SSA update operations. This centralized a bunch of code
- scattered through various passes (e.g. jump threading, lcssa, loop rotate,
- etc) for doing this sort of thing. The code generator has an similar
- <a href="http://llvm.org/doxygen/MachineSSAUpdater_8h-source.html">
- MachineSSAUpdater</a> class.</li>
-<li>The <a href="http://llvm.org/doxygen/Regex_8h-source.html">
- llvm/Support/Regex.h</a> header exposes a platform independent regular
- expression API. Building on this, the <a
- href="TestingGuide.html#FileCheck">FileCheck</a> utility now supports
- regular exressions.</li>
-<li>raw_ostream now supports a circular "debug stream" accessed with "dbgs()".
- By default, this stream works the same way as "errs()", but if you pass
- <tt>-debug-buffer-size=1000</tt> to opt, the debug stream is capped to a
- fixed sized circular buffer and the output is printed at the end of the
- program's execution. This is helpful if you have a long lived compiler
- process and you're interested in seeing snapshots in time.</li>
-</ul>
-
-
-</div>
-
-<!--=========================================================================-->
-<div class="doc_subsection">
-<a name="otherimprovements">Other Improvements and New Features</a>
-</div>
-
-<div class="doc_text">
-<p>Other miscellaneous features include:</p>
-
-<ul>
-<li>You can now build LLVM as a big dynamic library (e.g. "libllvm2.7.so"). To
- get this, configure LLVM with the --enable-shared option.</li>
-
-<li>LLVM command line tools now overwrite their output by default, before they
- would only do this with -f. This makes them more convenient to use, and
- behave more like standard unix tools.</li>
-
-<li>The opt and llc tools now autodetect whether their input is a .ll or .bc
- file, and automatically do the right thing. This means you don't need to
- explicitly use the llvm-as tool for most things.</li>
</ul>
-
</div>
<div class="doc_text">
<p>If you're already an LLVM user or developer with out-of-tree changes based
-on LLVM 2.6, this section lists some "gotchas" that you may run into upgrading
+on LLVM 2.8, this section lists some "gotchas" that you may run into upgrading
from the previous release.</p>
<ul>
-
-<li>
-The Andersen's alias analysis ("anders-aa") pass, the Predicate Simplifier
-("predsimplify") pass, the LoopVR pass, the GVNPRE pass, and the random sampling
-profiling ("rsprofiling") passes have all been removed. They were not being
-actively maintained and had substantial problems. If you are interested in
-these components, you are welcome to ressurect them from SVN, fix the
-correctness problems, and resubmit them to mainline.</li>
-
-<li>LLVM now defaults to building most libraries with RTTI turned off, providing
-a code size reduction. Packagers who are interested in building LLVM to support
-plugins that require RTTI information should build with "make REQUIRE_RTTI=1"
-and should read the new <a href="Packaging.html">Advice on Packaging LLVM</a>
-document.</li>
-
-<li>The LLVM interpreter now defaults to <em>not</em> using <tt>libffi</tt> even
-if you have it installed. This makes it more likely that an LLVM built on one
-system will work when copied to a similar system. To use <tt>libffi</tt>,
-configure with <tt>--enable-libffi</tt>.</li>
-
-<li>Debug information uses a completely different representation, an LLVM 2.6
-.bc file should work with LLVM 2.7, but debug info won't come forward.</li>
-
-<li>The LLVM 2.6 (and earlier) "malloc" and "free" instructions got removed,
- along with LowerAllocations pass. Now you should just use a call to the
- malloc and free functions in libc. These calls are optimized as well as
- the old instructions were.</li>
</ul>
+
+
<p>In addition, many APIs have changed in this release. Some of the major LLVM
API changes are:</p>
-
<ul>
-<li>Just about everything has been converted to use raw_ostream instead of
- std::ostream.</li>
-<li>llvm/ADT/iterator.h has been removed, just use <iterator>
- instead.</li>
-<li>The Streams.h file and "DOUT" got removed, use "DEBUG(errs() << ...);"
- instead.</li>
-<li><tt>ModuleProvider</tt> has been <a
-href="http://llvm.org/viewvc/llvm-project?view=rev&revision=94686">removed</a>
-and its methods moved to <tt>Module</tt> and <tt>GlobalValue</tt>.
-Most clients can remove uses of <tt>ExistingModuleProvider</tt>,
-replace <tt>getBitcodeModuleProvider</tt> with
-<tt>getLazyBitcodeModule</tt>, and pass their <tt>Module</tt> to
-functions that used to accept <tt>ModuleProvider</tt>. Clients who
-wrote their own <tt>ModuleProvider</tt>s will need to derive from
-<tt>GVMaterializer</tt> instead and use
-<tt>Module::setMaterializer</tt> to attach it to a
-<tt>Module</tt>.</li>
-
-<li><tt>GhostLinkage</tt> has given up the ghost.
-<tt>GlobalValue</tt>s that have not yet been read from their backing
-storage have the same linkage they will have after being read in.
-Clients must replace calls to
-<tt>GlobalValue::hasNotBeenReadFromBitcode</tt> with
-<tt>GlobalValue::isMaterializable</tt>.</li>
-
-<li>The <tt>llvm/Support/DataTypes.h</tt> header has moved
-to <tt>llvm/System/DataTypes.h</tt>.</li>
-
-<li>The <tt>isInteger</tt>, <tt>isIntOrIntVector</tt>, <tt>isFloatingPoint</tt>,
-<tt>isFPOrFPVector</tt> and <tt>isFPOrFPVector</tt> methods have been renamed
-<tt>isIntegerTy</tt>, <tt>isIntOrIntVectorTy</tt>, <tt>isFloatingPointTy</tt>,
-<tt>isFPOrFPVectorTy</tt> and <tt>isFPOrFPVectorTy</tt> respectively.</li>
</ul>
</div>
-
-
-<!-- *********************************************************************** -->
-<div class="doc_section">
- <a name="portability">Portability and Supported Platforms</a>
+<!--=========================================================================-->
+<div class="doc_subsection">
+<a name="devtree_changes">Development Infrastructure Changes</a>
</div>
-<!-- *********************************************************************** -->
<div class="doc_text">
-<p>LLVM is known to work on the following platforms:</p>
+<p>This section lists changes to the LLVM development infrastructure. This
+mostly impacts users who actively work on LLVM or follow development on
+mainline, but may also impact users who leverage the LLVM build infrastructure
+or are interested in LLVM qualification.</p>
<ul>
-<li>Intel and AMD machines (IA32, X86-64, AMD64, EMT-64) running Red Hat
- Linux, Fedora Core, FreeBSD and AuroraUX (and probably other unix-like
- systems).</li>
-<li>PowerPC and X86-based Mac OS X systems, running 10.4 and above in 32-bit
- and 64-bit modes.</li>
-<li>Intel and AMD machines running on Win32 using MinGW libraries (native).</li>
-<li>Intel and AMD machines running on Win32 with the Cygwin libraries (limited
- support is available for native builds with Visual C++).</li>
-<li>Sun x86 and AMD64 machines running Solaris 10, OpenSolaris 0906.</li>
-<li>Alpha-based machines running Debian GNU/Linux.</li>
</ul>
-
-<p>The core LLVM infrastructure uses GNU autoconf to adapt itself
-to the machine and operating system on which it is built. However, minor
-porting may be required to get LLVM to work on new platforms. We welcome your
-portability patches and reports of successful builds or error messages.</p>
-
</div>
<!-- *********************************************************************** -->
href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
there isn't already one.</p>
-<ul>
-<li>LLVM will not correctly compile on Solaris and/or OpenSolaris
-using the stock GCC 3.x.x series 'out the box',
-See: <a href="GettingStarted.html#brokengcc">Broken versions of GCC and other tools</a>.
-However, A <a href="http://pkg.auroraux.org/GCC">Modern GCC Build</a>
-for x86/x86-64 has been made available from the third party AuroraUX Project
-that has been meticulously tested for bootstrapping LLVM & Clang.</li>
-</ul>
-
</div>
<!-- ======================================================================= -->
href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
<ul>
-<li>The MSIL, Alpha, SPU, MIPS, PIC16, Blackfin, MSP430, SystemZ and MicroBlaze
- backends are experimental.</li>
-<li><tt>llc</tt> "<tt>-filetype=asm</tt>" (the default) is the only
- supported value for this option. The MachO writer is experimental, and
- works much better in mainline SVN.</li>
+<li>The Alpha, Blackfin, CellSPU, MicroBlaze, MSP430, MIPS, PTX, SystemZ
+ and XCore backends are experimental.</li>
+<li><tt>llc</tt> "<tt>-filetype=obj</tt>" is experimental on all targets
+ other than darwin-i386 and darwin-x86_64. FIXME: Not true on ELF anymore?</li>
+
</ul>
</div>
all <a href="http://llvm.org/PR879">inline assembly that uses the X86
floating point stack</a>. It supports the 'f' and 't' constraints, but not
'u'.</li>
- <li>The X86 backend generates inefficient floating point code when configured
- to generate code for systems that don't have SSE2.</li>
<li>Win64 code generation wasn't widely tested. Everything should work, but we
expect small issues to happen. Also, llvm-gcc cannot build the mingw64
runtime currently due to lack of support for the 'u' inline assembly
<div class="doc_text">
+<p>The C backend has numerous problems and is not being actively maintained.
+Depending on it for anything serious is not advised.</p>
+
<ul>
<li><a href="http://llvm.org/PR802">The C backend has only basic support for
inline assembly code</a>.</li>
<!-- ======================================================================= -->
<div class="doc_subsection">
- <a name="c-fe">Known problems with the llvm-gcc C and C++ front-end</a>
+ <a name="llvm-gcc">Known problems with the llvm-gcc front-end</a>
</div>
<div class="doc_text">
-<p>The only major language feature of GCC not supported by llvm-gcc is
- the <tt>__builtin_apply</tt> family of builtins. However, some extensions
- are only supported on some targets. For example, trampolines are only
- supported on some targets (these are used when you take the address of a
- nested function).</p>
+<p>llvm-gcc is generally very stable for the C family of languages. The only
+ major language feature of GCC not supported by llvm-gcc is the
+ <tt>__builtin_apply</tt> family of builtins. However, some extensions
+ are only supported on some targets. For example, trampolines are only
+ supported on some targets (these are used when you take the address of a
+ nested function).</p>
-</div>
-
-<!-- ======================================================================= -->
-<div class="doc_subsection">
- <a name="fortran-fe">Known problems with the llvm-gcc Fortran front-end</a>
-</div>
+<p>Fortran support generally works, but there are still several unresolved bugs
+ in <a href="http://llvm.org/bugs/">Bugzilla</a>. Please see the
+ tools/gfortran component for details. Note that llvm-gcc is missing major
+ Fortran performance work in the frontend and library that went into GCC after
+ 4.2. If you are interested in Fortran, we recommend that you consider using
+ <a href="#dragonegg">dragonegg</a> instead.</p>
-<div class="doc_text">
-<ul>
-<li>Fortran support generally works, but there are still several unresolved bugs
- in <a href="http://llvm.org/bugs/">Bugzilla</a>. Please see the
- tools/gfortran component for details.</li>
-</ul>
-</div>
-
-<!-- ======================================================================= -->
-<div class="doc_subsection">
- <a name="ada-fe">Known problems with the llvm-gcc Ada front-end</a>
-</div>
-
-<div class="doc_text">
-The llvm-gcc 4.2 Ada compiler works fairly well; however, this is not a mature
-technology, and problems should be expected.
-<ul>
-<li>The Ada front-end currently only builds on X86-32. This is mainly due
-to lack of trampoline support (pointers to nested functions) on other platforms.
-However, it <a href="http://llvm.org/PR2006">also fails to build on X86-64</a>
-which does support trampolines.</li>
-<li>The Ada front-end <a href="http://llvm.org/PR2007">fails to bootstrap</a>.
-This is due to lack of LLVM support for <tt>setjmp</tt>/<tt>longjmp</tt> style
-exception handling, which is used internally by the compiler.
-Workaround: configure with <tt>--disable-bootstrap</tt>.</li>
-<li>The c380004, <a href="http://llvm.org/PR2010">c393010</a>
-and <a href="http://llvm.org/PR2421">cxg2021</a> ACATS tests fail
-(c380004 also fails with gcc-4.2 mainline).
-If the compiler is built with checks disabled then <a href="http://llvm.org/PR2010">c393010</a>
-causes the compiler to go into an infinite loop, using up all system memory.</li>
-<li>Some GCC specific Ada tests continue to crash the compiler.</li>
-<li>The <tt>-E</tt> binder option (exception backtraces)
-<a href="http://llvm.org/PR1982">does not work</a> and will result in programs
-crashing if an exception is raised. Workaround: do not use <tt>-E</tt>.</li>
-<li>Only discrete types <a href="http://llvm.org/PR1981">are allowed to start
-or finish at a non-byte offset</a> in a record. Workaround: do not pack records
-or use representation clauses that result in a field of a non-discrete type
-starting or finishing in the middle of a byte.</li>
-<li>The <tt>lli</tt> interpreter <a href="http://llvm.org/PR2009">considers
-'main' as generated by the Ada binder to be invalid</a>.
-Workaround: hand edit the file to use pointers for <tt>argv</tt> and
-<tt>envp</tt> rather than integers.</li>
-<li>The <tt>-fstack-check</tt> option <a href="http://llvm.org/PR2008">is
-ignored</a>.</li>
-</ul>
+<p>The llvm-gcc 4.2 Ada compiler has basic functionality, but is no longer being
+actively maintained. If you are interested in Ada, we recommend that you
+consider using <a href="#dragonegg">dragonegg</a> instead.</p>
</div>
<!-- *********************************************************************** -->
projects / oota-llvm.git / blobdiff